This invention relates to an underwater viewing system for a remote piloted vehicle (RPV), and, more particularly, to a small lightweight viewing system wherein a source of illumination is provided to the RPV from a remote platform.
Although the present invention has general applicability for any viewing system, such as one which may be contained on an underwater RPV and used in preparation for salvage operations to observe the remains of the hull of a sunken ship or for viewing the underwater path in advance of own ship, it is especially well suited for deployment on a defensive-type torpedo.
Small torpedoes exist which have sufficient speed and maneuverability to intercept and destroy an incoming torpedo that is homing in on a base ship or other target. Such a chase--or defensive intercept torpedo requires a suitable sensing system which permits command and guidance information to be generated in response to the sensed information in order to accomplish its mission.
Sonar or acoustic based sensors require a significant delay time with respect to the anticipated speed of the incoming torpedo for an acoustic signal to propagate between the target or incoming torpedo and the acoustic receiver of the intercept or chase defensive torpedo. This delay time may detrimentally affect the response time of the chase torpedo. An optical sensor would overcome problems related to acoustical propagation delays because of the negligible propagation time of light through the transmitting medium with respect to the speed of the incoming torpedo.
An underwater viewing system should be capable of delivering sufficient light to the scene of interest for enabling sensing of the environment with the desired resolution and signal-to-noise ratio for any light returned from the scene. A significant problem for optical viewing are turbid conditions of the transmitting medium, such as may be experienced for large turbulent bodies of water, or water susceptible to contaminants or natural optical disturbances, such as silt from water runoff from land, is that the light being used to illuminate the scene is subject to back-scatter due, at least in part, to particulate matter that is disposed and suspended in the intervening transmitting medium between the source of light and the target. This phenomenon is analogous to requiring the viewing system to look through an atmospheric fog.
Prior optical systems have used range gated image intensifiers and an optical pulsed-radar type system to try to minimize the volume of water that is being analyzed and/or to establish the actual range to a target. Such techniques often require electronics and optics that may not conveniently be packaged in an intercept torpedo without potentially disturbing its maneuverability and response characteristics.